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排序方式: 共有1484条查询结果,搜索用时 15 毫秒
1.
Intracranial circulation: pulse-sequence considerations in three- dimensional (volume) MR angiography 总被引:2,自引:0,他引:2
The technique and feasibility of magnetic resonance (MR) angiography of intracranial vessels were studied in 35 healthy volunteers. Variations in image orientation, repetition time (TR), and flip angle were evaluated to determine their effects on flow-related enhancement. Gradient modifications--including echo time (TE), motion compensation, bandwidth, and field of view--were also studied in an effort to reduce motion-induced phase shifts. Results indicated that a FISP (fast imaging with steady precession) sequence with a TR of 50 msec, TE of 15 msec, velocity compensation in the read and section-select directions, acceleration compensation in the read direction, anisotropic volume, and a 1.25-mm partition thickness produced three-dimensional angiographic MR images that were accurate and reproducible in the depiction of the major intracranial vessels. Difficulties with field of view, persistent signal void secondary to higher-order motion, and spatial resolution remain major problems requiring additional study. 相似文献
2.
3.
4.
Maxillary sinusitis in adults: an evaluation of placebo-controlled double-blind trials 总被引:1,自引:0,他引:1
BACKGROUND: In general practice, acute sinusitis is frequently diagnosed
and treated with antibiotics. OBJECTIVE: This study aimed to determine the
evidence for the effectiveness of antibiotic treatment in acute maxillary
sinusitis in adults by assessing the methodological quality of
placebo-controlled double-blind randomized trials. METHOD: An evaluation by
four raters through a 35-item scoring-scale for internal and external
validity of all placebo-controlled double-blind randomized trials on acute
sinusitis found between January 1966 and July 1996. RESULTS: Eighty-five
trials were excluded because they were not placebo-controlled,
double-blind, randomized, or were carried out in patients with chronic
sinusitis or in children. The three remaining trials were performed in
different populations (one in general practice) between 1973 and 1978. Only
one study claimed superiority of antibiotic treatment. Different inclusion
criteria and major outcome measures were used by the authors. The
reliability of major outcome events was reported poorly or not at all and
in two studies outcome measures were clinically inappropriate. The studies
scored 30-62% of the maximum attainable score for internal validity and
10-20% for external validity. CONCLUSION: The effectiveness of antibiotic
treatment in acute maxillary sinusitis in a general practice population is
not based sufficiently on evidence.
相似文献
5.
6.
Various 2-(4-biphenoxymethyl)-5-arylamino-1,3,4-oxadiazoles were synthesized by cyclization of the corresponding 1-(4-biphenoxyacetyl)-4-substituted thiosemicarbazides. These compounds were characterized by their elemental analyses and infrared, mass, and nuclear magnetic resonance spectral data. All substituted thiosemicarbazides (100 mg/kg, ip) and cyclized substituted oxadiazoles (100 mg/kg, ip) possessed anti-inflammatory activity, as reflected by their ability to provide protection against carrageenin-induced edema in the rat paw which ranged from 28 to 68% and 36 to 76%, respectively. Cyclization of the substituted thiosemicarbazides, in general, resulted in an increase in the anti-inflammatory activity of their corresponding substituted oxadiazoles, with the exception of those containing 2,4-dimethyl and 3,4-dimethyl substituents in their molecular structure. Hydrocortisone (10 mg/kg, ip) and oxyphenbutazone (40 mg/kg, ip) were used as the standard reference drugs and these provided 45 and 53% protection, respectively. All compounds (1 mM) possessed antiproteolytic activity and the in vitro inhibition of trypsin-induced hydrolysis of bovine serum albumin ranged from 13 to 75% for substituted thiosemicarbazides and 39 to 70% for substituted oxadiazoles. There was no relationship between the anti-inflammatory activity of substituted thiosemicarbazides and substituted oxadiazoles and their antiproteolytic effectiveness. The low toxicity of these compounds was reflected by their high approximate LD50 values, ranging from 500 to 1000 mg/kg. 相似文献
7.
H Angus-Leppan GA Lambert J Michalicek 《Cephalalgia : an international journal of headache》1997,17(6):625-630
Co-existence of facial and occipital pain may occur in occipital neuralgia, migraine and cluster headache; suggesting convergence of trigeminal and cervical afferents. Such convergence has been shown in humans and other animals, but the site and extent of this are uncertain. In anaesthetized adult cats, the superior sagittal sinus and occipital nerve were stimulated electrically, and extracellular recordings made in the dorsolateral area of the upper cervical cord using glass-coated tungsten electrodes. Of 49 units in 10 cats, 33 (67%) had input from the superior sagittal sinus and the occipital nerve. Thirteen (27%) had superior sagittal sinus input and 3 (6%) had occipital nerve input. Convergent receptive fields were identified mechanically in 7 units. These experiments in cats show convergent input from occipital nerve and superior sagittal sinus on dorsolateral area units in two-thirds of cases studied. This experimental site of trigeminocervical convergence may relate to referral of pain in occipital neuralgia and other headaches. 相似文献
8.
In patients with PG-dependent renal function, NSAID administration
constantly reduces GFR and RBF in a dose-dependent fashion. In this
situation, the risk of overt acute renal failure is high and should be
taken into proper account. In contrast, the incidence of NSAID-related
renal structural alterations appears to be very low, yet the absolute
number of patients may be significant considering the wide use of such
drugs. Concerning the antiproteinuric effect of NSAIDs, the unfavourable
ratio risk/benefit does not seem to support their indication in proteinuric
nephropathies. The development of PGHS-2 selective inhibitors is promising,
and may open new therapeutical strategies in the treatment of the
progression of renal disease.
相似文献
9.
10.
K W Dabney S K Salzman T Wakabayashi J F Sarwark G X Gao A L Beckman W P Bunnell 《Spine》1988,13(5):472-477
The purpose of this study was to characterize the forces resulting from Harrington distraction of the spine in an experimental model of scoliosis in the rat, in order to establish both the similarity of this model to human scoliosis and identify potential force parameters that may be useful for clinical decision-making. Harrington distraction was performed in 36 rats that had been made scoliotic 9-12 weeks earlier by the method described in the previous paper. Distractions were carried out in discrete and timed steps until separation of the vertebral laminae (mechanical failure) occurred at the upper hook site. Distractive forces were monitored continuously by a strain gauge mounted on the tension side of the upper arm of the outrigger. The resulting data were compared among the various curvature groups. The relationship between the length of distraction and the maximum force produced was similar for all animals regardless of curvature. This relationship was quadratic and was characterized by an inflection point where forces increased rapidly with each distraction. The amount of distraction necessary to reach both the inflection and failure points differed only for curves above 100 degrees. The amount of force required to reach failure was lower for curves above 75 degrees. Curves above 50 degrees had a lower percent correction at the inflection point. Bending and tensile forces were calculated by vector analysis. Axial load efficiencies were greater for curves above 50 degrees, as evidenced by increased bending forces in these animals. The viscoelasticity of the spine decreased after inflection in all animals.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献